What is a Plugin?
Firefox requires plugins in order to read or display special content from the websites. Plugins are programs that are integrated into Firefox that allows websites to provide content to you. Such content includes flash videos, java games and streaming video from the Internet. Examples of plugins are Flash, RealPlayer, and Java. Plugins are a necessary component to truly access the Internet's interactive stuff.
What is Current Version Plugin?
Firefox plugins should be updated to latest version. Firefox plugin check page will find the latest update of plugins. Having said that, There are few plugins will be given as unknown plugins if firefox is unable to recognize. These unknown plugins should be updated manually by finding the current version plugin in search engine. Any plugin update can be found by prefixing keyword current version plugin in search engine.
Before You Install
Close Firefox before installing plugins
Firefox should be closed before running any plugin installation programs, as existing files may be overwritten during the installation process.
Using XPInstall to install plugins
Some plugins are available as XPInstall packages (XPIs), the same format as that for extensions. Where XPIs are available, it is recommended you use them as they often install the plugin automatically without you having to restart Firefox. After the XPI has finished installing, you should restart your browser.
Checking which plugins you have installed
To check what plugins you have installed, simply type about:plugins in the Location bar. This page will show which plugins are installed, what file types they are associated with and if the plugin is enabled or disabled.
Adobe PDF Reader
In order to read .pdf files, you need to install a pdf reader. Adobe Reader, one of the more popular software, can do this. Simply go to Adobe's official site and download Adobe Reader. With Firefox closed, install Adobe Reader and it will also install the plugin necessary for Firefox to view PDF files. No other steps are necessary. Firefox will now open all PDFs from within a Firefox tab.
If you install Adobe Reader after Firefox, Adobe Reader will automatically select the right plugin. If you already have the latest version of Adobe Reader installed then Firefox will automatically use the plugin. Some people have problems with the Adobe Reader plugin in Firefox. The explanation and solution is here.
The Java Plugin is part of the Java Runtime Environment (JRE, for short). The JRE installer will install the Java Plugin for Netscape 7.2 and Mozilla automatically.
To get the it simply go to java.com and click the "Download Now!" button to download and install the latest JRE.
Macromedia Flash Player
When you encounter a site that makes use of Flash graphics, a yellow bar will appear at the top of the page telling you that there is a missing plugin preventing you from viewing all the content on the current page. Click on Install Missing Plugins button and the Mozilla Plugin Finder Service will appear automatically. After accepting the User Agreement from Macromedia, the necessary components to view Flash will be installed.
Alternately, you may install Macromedia Flash Player (without having to go to a site) by installing the plugin manually. Simply go here and click on the Macromedia Flash Player 8.0 link.
Macromedia Shockwave Player
Simply go to the Macromedia Shockwave site and download the plugin. When you are installing it, Firefox will appear in the list of browsers that you can install the plugin for. (Remember, Firefox should be closed when installing).
Quicktime Player (Windows & Mac)
Simply go to Apple's (the developer of Quicktime) website and download Quicktime. Installing Quicktime will install the appropriate plugin in order for Firefox to view .mov files.
Simply go to Real's (the developer of RealPlayer) website and download the program. The RealPlayer installer will automatically detect your browser's plugins folder and install the plugin.
A list of your installed plugins can be obtained from about:plugins. As a general rule, to remove a plugin, you remove the file listed in about:plugins for it. Typically a .dll file.
On a XP machine this can typically be found at c:\Program Files\Mozilla Firefox\plugins